First, solve one of the equations for one of the variables. It really doesn't matter which equation or which variable. You probably will want to choose the way that's the easiest. I'm going to start by solving the 2nd equation for y:

Now, substitute this into the 1st equation wherever you see a y, and then solve for x:

Now, plug this into the altered version of the 2nd equation:

The answer is (1, 2). You want to try your other example now?

EDIT: Too slow! ;)

Aug 10th 2010, 09:59 PM

mafai44

thank you! does anyone know solving for elimination?

4x=15+3y
-6/5x+y=-17/5

Aug 10th 2010, 10:01 PM

Prove It

I can't really read that...

Is it

?

Aug 10th 2010, 10:04 PM

mafai44

yes the 6/5x , the x is for both the 6 and 5 not just the 5.. not even sure if that matters but you have it right.

Aug 10th 2010, 10:12 PM

Prove It

Obviously it's not right if it's meant to be

since , not ...

Anyway...

Multiply the second equation by ...

.

Now add the equations together

.

Substituting into the first equation

.

So is the solution.

Aug 10th 2010, 10:19 PM

mafai44

Quote:

Originally Posted by eumyang

5x-7=-y
2x-y=0

First, solve one of the equations for one of the variables. It really doesn't matter which equation or which variable. You probably will want to choose the way that's the easiest. I'm going to start by solving the 2nd equation for y:

Now, substitute this into the 1st equation wherever you see a y, and then solve for x:

Now, plug this into the altered version of the 2nd equation:

The answer is (1, 2). You want to try your other example now?

EDIT: Too slow! ;)

yeah if you can help me out with the other example that would be great.. this is one part of math that i do not like haha

Aug 10th 2010, 10:20 PM

mafai44

double posted by accident sorry

Aug 11th 2010, 05:12 AM

eumyang

OP: Prove It's point is that you have to be careful with notation. Ideally, you should learn LaTeX so that it's not ambiguous when you type . 6/5x is really read as . If you are not using LaTeX and you want to indicate the fraction 6/5 times x, use parentheses: (6/5)x.